This article is from
Journal of Creation 37(1):16–17, April 2023

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Equivocal carbon dating of ancient footprints in Tularosa Basin, New Mexico

by Andrew Sibley

Image: National Park Service, Wikimedia / Public Domain

Scientists have discovered human footprints in the Tularosa Basin of New Mexico, USA; more specifically in the White Sands National Park. Recently assigned radiometric dates of these footprints conflict with the previous understanding of human occupation of North America based on genetic reconstruction studies.

Tularosa Basin is enclosed by mountains, so no water can flow out of it. Instead, water evaporates, thus forming several dried-out lakes, known as playa lakes, such as Lake Lucero (formerly ancient Lake Otero) (figure 1). The ancient lakebed is known for its selenite or gypsum crystals (CaSO₄·2H₂O). In this environment multiple tracks of human footprints have been preserved (figure 2) alongside evidence of large mammal habitation (also primarily from footprints) such as mammoths and giant sloths, and predators such as lions and wolves. When the footprints were made the environment at this site was evidently much wetter and better suited for human occupation.

Image: National Park Service, Wikimedia / Public Domain

Ice Age footprints

These footprints have recently been conventionally dated to 23–21 ka before present (BP), which the researchers believe correlates with the period of the Ice Age in North America (the Late Pleistocene). The dates have been determined by the stratigraphy, together with carbon dating of co-located seeds from freshwater plants. The plant in question, Ruppia cirrhosa, more commonly known as spiral ditchgrass or spiral tasselweed, grows today in fresh or brackish shallow water, with its foliage sourcing carbon from the water, not the air (figure 3). The researchers discounted hard water or reservoir effects¹ as having any significance on their findings, partly because of the shallow nature of the water in which the plants grew, which would have led to the likely exchange of atmospheric carbon into the water over time. The presence of so many footprints suggests it was a more hospitable place (i.e. wetter) for mammalian life to thrive than the current desert environment allows. Uranium/thorium dating (²³⁰Th/U) of gypsum from boundary strata gave ‘ages’ of between 100 and 25 ka, but the authors narrowed this down through the selection of representative data to 25.6 ± 4.4 ka.²

Image: Kristian Peters, Wikimedia / CC BY-SA 3.0

As a result of this ancient timeframe, the scientists proposed that humans had colonized North America from Asia during the Last Glacial Maximum, which is earlier than the standard narrative allows. The official narrative is that human settlers had not arrived in this part of North America before 20 ka. This estimate has been determined through studies of ancient DNA from human fossils, together with assumed rates of genetic change. If the footprints are older, it would invalidate such genetic reconstructions.³

Disagreement over carbon dating

However, other researchers were far less certain and called into question the outcome of the carbon dating. They argued that the ground water in the lake would not have reached (near) equilibrium with atmospheric carbon dioxide, and therefore would lead to false readings. In attempting to re-evaluate the age of the footprints, these scientists carbon-dated more recent seeds of the same spiral ditchgrass that were collected at Malpais Spring in 1947. They found that the seeds contained very low levels of carbon-14, proposing that the carbon in the seeds had not been sourced from the air, rather from the ground water, which contained very little carbon-14.

Measurements of carbon-14 of this specimen were recorded at about 7.4 ka, and yet the seeds were only 75 years old, an error of two orders of magnitude. If applied to the previous samples, it would revise the dating of human footprints downwards, from 23–21 ka to a more ‘acceptable’ 15–13 ka, which is in accord with the standard model of when humans are believed to have arrived in North America.⁴ The researchers have called for further studies, including carbon-dating of biological material from atmospheric sources, and optically stimulated luminescence dating of the lake sediment quartz.³

What does this tell us about the accuracy of dating?

This example shows that radiometric dating can give very different results, and the selection of dating preferences is driven by the needs of the secular narrative. In other words, it is another example of the need to fit the data to protect the official model. While carbon dating can be fairly accurate for dating trees, where the carbon has been taken from the atmosphere, much larger errors arise when water is involved; for example, with the marine reservoir effect and the hard water effect.⁵ There is clearly uncertainty with the example of Lake Lucero—the fact that seeds which are only 75 years old can be dated to 7,400 years bp due to hard water effects demonstrates the margin of error. This effect has previously been known to give excessive ages; for example, pottery fragments used to cook fish have been mistakenly ascribed ages 2,000 years older than they really are.⁶

While the later researchers (Oviatt et al.⁴) seek to hold to the standard model of human migration, their work highlights just how uncertain dating methods can be, and it is a serious challenge to the wider secular narrative. Creation scientists would interpret the human footprint data as that of the post-Babel dispersion of people from the Middle East during the later stages of the Ice Age, with a timeframe of around 4,000 years before present.

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